Seed viability depends upon type of seed and storage conditions. Some seeds, when stored in airtight containers and protected from harsh light can remain viable for several years; others begin to lose viability within a year. The only way you will know for sure is to do a viability test. Simply place a few of the seeds on a damp papertowel, set it in a plastic bag and put in on your kitchen counter. Check the seeds in about a week. Viable seeds will begin to sprout. You can still plant them. The number of sprouting seeds subtracted from the number of seeds that did not sprout will give you the germination potential. So, if you placed 10 seeds in the damp papertowel and all 10 sprouted, you'll probably have 100 percent germination. If only 5 of the 10 seeds sprouted, you can expect only 50 percent germination. If this is the case, double up on the number of seeds you plant and your garden should still grow nicely for you. Enjoy!